Boom for excavating machines



DCC. 17, 1929. R R DQWNIE BOOM FOR EXCAVATING MACHINES Filed Deo. 3l, 1927 lll,... lill-9:

ATTORNEY INVENTO Patented Dec. 17, 192@ STATS 'arnese carena carica ROBERT REX DOWN IE, 0F BAVER FALLS, PENNSYLVANIA, ASSIGNOR TO KEYSTONE :DRILLER COMPANY, OF BEAVER FALLS, PENNSYLVANIA, .A CORPORATION OF PENNSYLVANIA BOOM FOB. EXCAVATING MACHINES Application led December 31, 1927. Seri'al No. 244,009.

rl'his invention relates to the construction of booms for excavating machines, particularly for skimmer scoops and ditching inachines, of the types disclosed'. in my prior Patents Nos. 1,586,390 and 1,511,114. Among other objects, the invention aims to provide a boom which has torsional resilience, with resistance Jto-vertical bending stresses, which is not prohibitively heavy or expensive to manufacture, and which is far less subject to fracture than booms as hereto ore con* structed.

In the accompanying drawings showing one form of boom embodying the invention,-

F ig. 1' is a side elevation of a boom;

Fig. 2 is a top plan view of the same;

Fig. 3 is a section on line 31-'3 of Fig. 4;

Fig. 4 is an enlarged section on line 1 -1 of Fig. 1;

Fig. 5 is an enlarged section on line 5-5 of Fig. '2; and

Fig. 6 is an enlarged section on line 6-6 of Fig. 1.

In the operation of excavating machines of the type decribed in the above named patent, the boom'is constantly being subjected to bend-ing and torsional stresses, which may be rapidly reversing stresses. To provide for the utmost strength with a minimum amount of metal, the booms have usually been made of two ill-beams or the like joined together by riveted cross-pieces. It has been found, however, that such booms frequently break, even when built of extra heavy beams; and as the 'machines are useless until supplied with new booms, `large losses are sometimes suffered by the contractors. The present invention provides a boom of ample strength and ofl'the proper torsional resilience, without any lines of weakness caused by the provision of numerous rivet holes; and, in practice, over a period of nearly two years, has

eliminated breakage of the beams.

Refeiring particularly to the drawings, there is shown a boom embodying the invention and capable of being used with a. skimmer scoop, a ditcher, andvarious other kinds of excavating machines. The boom is shown as made lup of two spaced Iii-beams 10, which contrary to usual practice have no rivet or bolt holes throughout their entire lengthexcept near the extremities, which are not subjected to the bending and twisting deformations that the middle portion is subjected to.

At intervals, the I-beams 10 are joined by spacing cross-pieces 11, which in the illustrative embodiment are entirely within the confines of the boom, and are welded at their opposite ends to the inside faces of the webs of the I-beams. "As lbest shown in Figs. 4 and 5, each of the two crosspieces 11 has enlarged feet 12 at each end, whose Contact area is large as compared to the sectional area of the intermediate portion or web of the crosspiece. To permit very slight movement of one I-beam relative to the other, although united by the cross-pieces, each of the crosspieces is materially reduced in cross-section at or substantially at its middle. To strengthen the welded joints, each foot 12 has its perimeter materially increased, for example, by a series of wide notches 13. As the cross-pieces are preferably of elongated cross-section and hence are more resistant to bending in one direction than in the other, I prefer to arrange them more or less as indicated in Fig. 1, wherein two of thel crosspieces are substantially parallel to the longitudinal axis of the boom, a third lies at an oblique angle to said axis, and two others, located about half-way between the middle of the boom and its outer end are slightly disalined from said axis. Experience has proven thatsuch a boom has the necessary strength and resilience, and can be twisted and subjected to very heavy bending stresses without permanent deformation, and without fracture. Obviously, many forms and a' varying number of cross-pieces may be used.

In both the skimmer scoop and ditcher,

at the outer end of the boom, and the lother I support-ed well above the boom close to the outer end. In the case of the ditcher, an

intermediately located sheave is used to guide the hauling line as shown in Patent 1.511,114. F or illustrative purposesa the boom in Fig. 1 is shown equipped 'with both end sheaves for the skimmer scoop, and the intermediate sheave for the ditcher; but in practice the intermediate sheave is removed in skimmer work` vvhile the end sheaves are removed for the ditcher. According to the invention, all three shea-ves are easily installed and removed Withoutproviding bolt holes in the boom, which would seriously weaken it7 particularly if located at an intermediate point.

Referring to Figs. 1 and 2. three pairs of pads 14, 15, 16 are shown, Welded to the top surfaces ofthe I-beams, and arranged longitudinally of the boom. ll the pads have tapped holes for receiving cap-screws 1T which secure the sheave bearings 18 or the link plates 19 to the pads; but as shown in Figs. 3 and 4, the cap-screw holes do not enter the lbeams. and therefore the boom section is not impaired. The bolt holes 2O (Fig. 1) which are provided in the webs for attachment of extensiony irons (shown in Patent 1.511,114) are located in a region not critically stressed so that' the slight weakening ofthe boom resulting` therefrom is of no consequence.

The l-beams may be connected together by one or more members 21, and between 'the pads 15 and 16 there may be one or more shaped connecting members 22 (Fig. 2) welded to the top and/or bottom flanges of the bearns, or an additional cross-piece 11 may be welded within the boom.

While I have described and shown a boom made up of two lbeams, obviously other structural shapes might also be employed for the longitudinal mem ers. I

l have mentioned only skimmer scoops and ditehers as types of excavating machines with Which the improved boom may be used. It'will be'understood that the boom may be employed with other excavating machines7 \for example, drag-line excavators. How ever, the invention is believed to be most useful and valuable when embodied in structures adapted for skimmer scoops and ditchers b"w cause of the peculiarly rigorous requirements of booms for such machines.

Obviously the present invention is not restricted to the particular embodinient thereof herein shown and described. ll/loreover, it is not indispensable that all the features of the invention be used conjoii'itly7 since they may be employed advantageously in various combinations and sub-combinations- W hat l claim is 1. A.. boom for excavating machines cornm prising a unitary structure of two soaced., parallelbeams; and spacers with enlarged ends extending between said beams and 'welded at their ends to each of the beams;-

said spacers having intermediate portions whose sections are considerably smaller than the areas of said enlarged ends.

2. t boom for excavating machines comprising a unitary structure of two spaced beams; and spacers extending between and welded at their ends to the webs of the beams; said spacers having a reduced cross-section at substantially their mid-portions and having enlarged feet at their ends for attachment to the beams. 3. t boom for excavatingmachines comprising a unitary structure of two spaced beams; and spacers extending between and welded at their ends to the beams; each of the spacers being located within the contines of the boom and being secured to the opposed inside faces of the beams, some of the spacers being of elongated cross-section and extending at oblique angles to the longitudinal axis of the boom.

4. lli-boom for excavating machines comprising a unitary structure of two spaced beams; and spacers extending between and welded at their ends to the beams; said spacers extending in planes which lie at different angles relative to the longitudinal axis of the boom, and having a reduced-crosssection at substantially their mid-portions and enlarged feet at their ends for attachment to the beams.

5. A boom for excavating machines comprising two maj or longitudinal members ;and cross-pieces arranged at intervals along the length of the boom and welded at their opposite ends to said members; one or more pairs of pads welded to said members and having bolt holes or the like; and one or more'sheave mountings connected to one or more pairs of pads by bolts or the like; the construction being such that the sections of the major members are not impaired by the provision of holes for the attachment of the sheaves.

1ln testimony that l claim the foregoing as my own, I have hereto allxed my signature.

ROBERT REX noWNin. 

